Telecommunication companies running PSTNs (Public Switched Telephone Networks) and PLMNs (Public Land Mobile Networks) are in the business of providing communication services and in doing so provide built-in intelligence in the form of “IN services” such as 800 number services and call forwarding, for instance.
The basic service provided by a PSTN (Public Switched Telephone Network) is the interconnection of two telephones (that is, setting up a bearer channel between the telephones) according to a called-party telephone number input at the calling-party telephone. FIG. 1 is a simplified representation of a PSTN providing such a service. In particular, customer premises equipment, CPE, 10 are connected through an access network 11 to switching points, SPs 12 (only one SP is shown in FIG. 1). The SPs 12 form nodes in an inter-exchange network 13 made up of interconnecting trunks 14 and SPs that are controlled by control entities 15 in the SPs. The control effected by the control entities 15 is determined by signalling inputs received from the CPEs and other SPs, and involves call setup, maintenance and clearance to provide the desired bearer channel between calling CPE and called CPE. Conceptually, the PSTN may be thought of as a bearer network and a control (signalling) network, the function of the latter being to effect call control through the bearer network, namely the control of setup, maintenance and take down of bearer channels through the bearer network; in practice, the bearer and signalling networks may use the same physical circuits and even the same logical channels.
Thus, where the CPE 10 is a traditional dumb telephone, control signalling between the CPE and its local SP is in-band signalling, that is, the signalling is carried on the same channel as used for voice; this signalling is interpreted and converted at the SPs 12 into signalling between SPs that uses a dedicated common-channel signalling network 16. Common-channel signalling network is generally implemented using the SS7 protocol suite. Modern SPs use the ISUP (ISDN User Part) SS7 protocol for inter-exchange call control signalling.
In addition to basic call handling, an SP may also serve to provide what are called IN (Intelligent Network) services; in this case the SP is termed a service switching point, SSP. An SSP provides a logical function referred to as a Service Switching Function (SSF) 25, that is it is arranged to suspend call processing at defined points-in-call upon particular criteria being met, and to delegate the continuation of call processing to a service control subsystem providing a service control function (SCF) 17 either in the form of a service control point, SCP, or an Adjunct. An Adjunct would be directly associated with an SSF 25 whilst an SCP and SSF 25 communicate with each other via an extended common channel signalling (CCS) network 16 that may include signal transfer points (STP) (not shown). The SCF 17 may be associated with more than one SSF 25. SCF 17 provides a service logic execution environment (SLEE) 20 in which instances of one or more service logic programs (SLP) 21 can execute. The SLEE 20 and SLP 21 together provide service control functionality for providing services to the SSF 25.
Service logic running in an SCP or Adjunct will generally make use of subscriber information stored in a service data function (SDF) 22 that may be integral with the SCP or partially or wholly separate. The service data function (SDF), like the service control function (SCF) forms part of the service control subsystem of the PSTN. It may be noted that some or all of the service control function may be built into the PSTN switches themselves.
In operation, when the SSF 25 receives a call, it examines internal trigger conditions and, possibly, user information (eg dialed digits) to ascertain if the call requires a service to be provided by the service control point 17; the checking of trigger conditions may be carried out at several different points in call processing. Where the SSF 25 determines that a service is required it messages the SCF 17 requesting the desired service and sending it a logic representation of the call in terms of its connectivity and call processing status. The service control subsystem then provides the requested service and this may involve either a single interaction between the SSF and service control subsystem or a session of interactions.
In addition to the SCF 17, the network illustrated in FIG. 1 may include an Intelligent Peripheral (IP) or Specialized Resource Function (SRF) 23. The term SRF, which refers to the logical as opposed to the physical entity, will be used in the following description to refer to this element. SRF 23 has bearer-channel connectivity to one or more SSFs 25. SRF 23 provides resources needed to exchange information with an end user, such as voice announcements and DTMF digit collection capabilities (this type of non-signalling information intended to be passed over a bearer-channel to/from the end user is referred to below generally as “content”). In known implementations, these resources are managed and controlled by a resource control execution environment (RCEE) of the SRF 23 in response to input received from an SSF 25. Such input may result, for example, from SCF 17, during execution of an SLP 21, requiring a voice announcement to be played to an end user; in this case the service control subsystem passes this requirement to the SSF concerned which sets up a bearer channel to the SRF 23 and commands the SRF to play the required announcement. It is also possible to arrange for the service control subsystem to communicate directly over the CCS network with an SRF rather than going though an SSF 25.
SRF functionality and resources may also be provided within a service node (SN) which like an IP has bearer-channel connectivity to an SSF; however, an SN additionally includes an execution environment, similar to SLEE 20, for running service logic programs. An SN can thus provide a range of services virtually autonomously once an SSF has switched through a call to the SN; in particular, an SN is apt to provide services such as voice mail, automated attendant and fax server, all of which require substantial transfer of content to/from an end user. To the extent that an SN can execute specific types of SLPs, it forms part of the service control subsystem of the network.
The above-described model for the provision of IN services in a PSTN can also be mapped onto PLMNs (Public Land Mobile Networks) such as GSM and other mobile networks. Control signalling in the case of a mobile subscriber is more complex because in addition to all the usual signalling requirements, there is also a need to establish where a call to a mobile subscriber should be routed. Thus in GSM for instance, the service data function (SDF) is largely located in a system named a Home Location Register (HLR) and the service control function in a-system named a Visitor Location Register (VLR) that is generally associated on a one-to-one basis with each SSF (which in GSM terminology is called a Mobile Switching Centre, MSC).
Because subscribers are mobile, the subscriber profile is transported from the HLR to whichever VLR happens to be functionally closest to be mobile subscriber, and from there the VLR operates the (fixed) service using the subscriber profile and interacts with the SSF. The HLR and VLR thus constitute a service control subsystem similar to an SCP or Adjunct with their associated databases.
The above-described general architectural framework has proved generally satisfactory and many voice services have been successfully deployed around the world using large, fault-tolerant computer systems which provide services for hundreds of thousands or even millions of subscribers.
In parallel with the implementation of IN telephone infrastructure, the Internet and the, more particularly, the World Wide Web (WWW) have grown rapidly to become the primary electronic information distribution service in terms of spread, availability and richness of information content and a ubiquitous vehicle for on-line commerce and services.
One important factor in the success of the WWW has been the use of markup languages, and particularly the HyperText Markup Language (HTML), for representing the makeup of documents transferred over the WWW, and the availability of powerful graphical Web browsers for interpreting such documents in a client terminal to present them to a user. Coupled with this technologies have been developed for dynamically generating the documents at the server side in conjunction with back-end business applications.
However, it is in many situations far more convenient to have access to a telephone than to have access to a computer with an Internet connection. As a result, there has been increasing interest in being able to access web-based or web-like services from telephones.
Voice Browsers, such as that provided by the HP Opencall Media Platform, allow access to web-based or web-like services from any telephone by using speech synthesis, pre-recorded audio, and speech recognition. A voice browser is interposed between a user and a voice page server and may access the voice page server using http over the Internet. A voice page server holds voice service pages (text pages) that are marked-up with tags of a voice-related markup language (or languages), such as the Voice eXtensible Markup Language (VoiceXML). When a VoiceXML page is requested by the user, it is interpreted by the voice browser and output intended for the user may, for example be passed in text form to a Text-To-Speech (TTS) converter which provides appropriate voice output to the user. User voice or DTMF input can also be decoded or recognised to text and passed back to the server. Of course, voice service pages can also be dynamically generated at the server-side.
The present invention is directed to facilitating the integration of modem voice-browser platforms, and other types of media gateways, in pre-existing IN-based networks.